The invention relates to a process for the application of liquid, pasty or plastic substances, in particular of thermoplastics, to a substrate, the substance being melted, heated and applied to the substrate through a perforated cylinder, it adhering to the said substrate over a certain distance before it is drawn off, as well as an apparatus for this.
German Offenlegungsschrift 3,638,307 discloses such a process and such an apparatus, the nozzle mouth being followed inside the metal cylinder by an air nozzle, which forms a nozzle gap bounded by lips towards the metal cylinder. Furthermore, outside the metal cylinder there are arranged cooling and heating sections, before the substrate runs through a pair of calendar rolls. In this case it has been found in practice that, at different temperatures of the coating substance, a different tension has to be exerted on the substrate in order to lift the substrate off the perforated metal cylinder.
The object of the present invention is to improve substantially the temperature control for the coating substance and, furthermore, also to ensure an improvement in the application of the coating substance as well as in the handling of the coating head when the apparatus is switched off.